Joe,

Check into the Biela website and see if they have a prop in the 23-8 size. It will be a touch less than the MSC but miles ahead of the NX. Pricey and slow to get here, but worth it if they have the size you need. Also try Aircraft International and 3W as possible sources. Although the 23-8 MSC may appear to work well on the 50cc motors, MO is they will load up the engine too much, heating up the top of the piston to undesireable levels.